A Scalable Fishbone Nanowire Array (FINE) for 3D Quasi‐Intracellular Recording in Intact Brains

Abstract Intracellular recordings provide unique access to the submillisecond neuronal membrane potential changes, revealing dynamics that orchestrate cellular, local, and large‐scale brain activity. However, technical requirements limit the scalability of intracellular recordings to large populations of neurons, especially within intact brains. To overcome this limitation, a Fishbone Intracellular Nanowire Electrode (FINE) is developed with ultra‐sharp nanowire tips strategically integrated at slanted angles along an implantable shank to record 3D intracellular potentials from ensembles of neurons in intact brain. A novel fabrication process is developed to integrate reverse‐angled platinum silicide (PtSi) nanowires to preserve the structural integrity of FINE during insertion. As‐implanted or sub‐micron retraced FINE spreads the PtSi nanowires away from the shank to establish intimate nanowire‐neuron interfaces that yield quasi‐intracellular potentials. Comparative analyses of nanowire recordings versus adjacent planar recordings on the same shank validate their distinctive quasi‐intracellular recording characteristics. The scalability of FINE is demonstrated to a 3D 24‐shank array with 594 nanowires and 430 planar contacts and successfully identified quasi‐intracellular potentials across 127 distinct nanowires in the intact brain. FINE's 3D quasi‐intracellular recording holds the potential to unlock detailed investigations of the intricate ionic potential fluctuations and patterns of transmembrane potentials that drive behavior and cognition.